Occupational studies are conducted to identify and quantify chemical and other causes of cancer and to understand mechanisms of carcinogenesis. Etiologic investigations utilize sophisticated industrial hygiene methods to assess occupational exposures and biochemical components to characterize exposure-response patterns, to elucidate mechanisms of carcinogenic action, and to evaluate individual susceptibility factors. Methodologic studies are designed to improve study techniques and to provide direction for future research. Major etiologic investigations focus on working populations exposed to benzene, other organic solvents, acrylonitrile, formaldehyde, diesel exhausts, combustion products, electromagnetic fields, pesticides, and silica. Findings linking cancer with occupational exposures included an excess of nasopharyngeal cancer among workers exposed to formaldehyde; breast cancer and early life exposure to polycyclic aromatic hydrocarbons; stomach cancer and employment in the leather and metal industries; and pancreas cancer and work as truck drivers, railroad workers and in the chemical industry. Other studies found a mortality deficit among farmers and their wives and associations with midlife symptoms and women's exposure to solvents at the workplace. Reviews of risks of disease and injury among agricultural populations and the need for occupational studies of cancer were also published. Ongoing projects to evaluate occupational exposures include case-control studies of bladder cancer in Spain and New England, lung cancer in Russia, renal cancer in Eastern Europe, renal cell cancer in the United States, mesothelioma in the United States, non-Hodgkin's lymphoma in the United States, lung cancer in China, and breast cancer, endometrial, and ovarian cancer in Poland. Ongoing cohort studies of occupational groups include miners with exposure to diesel exhausts; farmers with exposure to pesticides and other agricultural chemicals; women in many occupations in Shanghai; Coast Guard marine inspectors exposed to solvents; shipyard workers exposed to asbestos, paints and welding fumes; and cohorts of industrial workers with exposure to benzene, acrylonitrile, formaldehyde, and solvents.